While the green anaconda or water boa (Eunectes murinus) may not hold the title of the worlds’ longest snake—coming second to the reticulated python—its huge girth means that it is undoubtedly the largest. During the 19th and 20th century, many accounts of giant specimens of anaconda were reported. While almost certainly exaggerations, it is possible that in remote, deep rainforest rivers, under optimum conditions of prey availability, the green anaconda may grow to record proportions. The green anaconda is well-adapted for its semi-aquatic lifestyle, with its eyes and nostrils positioned on top of the head, enabling the snake to see and breathe while the rest of the body is submerged. The colouring of the body provides excellent camouflage, with olive green upperparts boldly marked with pairs of dark ovals on either side of the spine, which are sometimes fused. The flanks are also marked with smaller, light-centred dark spots, while the head, which is relatively small compared to the thick body, bears a distinctive stripe, which runs from the rear edge of the eye, diagonally downwards to the back of the head. The stripe is edged with black and varies in colouration, from greenish to orange. In addition to its gigantic proportions, another remarkable feature of the green anaconda is that it exhibits the greatest size difference between the sexes of any terrestrial vertebrate. The female dwarfs the male and is almost five times heavier.
